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Tong X.C.,Laird
Springer Series in Advanced Microelectronics | Year: 2014

The characterization of optical waveguides is a very important and essential step in any waveguide design and fabrication process. It is necessary to evaluate and confirm that the fabricated waveguide exhibits characteristics as designed. During materials selection and waveguide design, accurate measurements of key characteristics should be done with suitable methods. The major characteristics may include refractive index, layer thickness, optical coupling, optical loss, and nonlinear properties. Experimental evaluation and validation are necessary since these characteristics are rather difficult to determine theoretically. Such measurements provide important fundamental data to evaluate whether the waveguide is appropriate for integrated optical interconnection system, and use to specify the reason for the characteristics degradation. Therefore, the evaluation of the waveguide characteristics serves as a feedback to the design and the fabrication process, which is crucial for the modification and optimization of the waveguide performance. In this chapter, a series of optical waveguide characterization techniques will be elaborated. © Springer International Publishing Switzerland 2014. Source


Tong X.C.,Laird
Springer Series in Advanced Microelectronics | Year: 2014

Semiconductor optical waveguides are a very important part of modern integrated optoelectronic systems, especially for electrically active devices. Applications range from semiconductor lasers, optical filters, switches, modulators, isolators, and photodetectors. Semiconductor waveguides have many advantages especially for use in slow light applications. They offer a significant enhancement of interaction length that, to first order, scales with the possible delay. With a tight confinement of the optical mode, the required optical power can be drastically reduced while the mode overlap with the active material is strongly enhanced. The use of semiconductor material is of particular interest since it offers compactness and enables for monolithic integration into optoelectronic devices using well established processing techniques. Furthermore, semiconductors are attractive since the operating wavelength, to a large extend, can be designed while performing with bandwidths in the GHz regime that is well suited for communication signals. Based on III-V, II-VI, or IV-VI group elements, two semiconductors with different refractive indices are generally synthesized for fabrication of optical waveguides. They must have different band gaps but same lattice constant. An attractive feature of the binary compounds is that they can be combined or alloyed to form ternary or quaternary compounds, or mixed crystals, for varying the band gap continuously and monotonically together with the variation of band structure, electronic, and optical properties. The formation of ternary and quaternary compounds of varying band gaps also enables the formation of heterojunctions, which have become essential for the design of high performance electronic and optoelectronic devices. This chapter will give a brief review about fundamental theory, semiconductor materials, and fabrication technologies of various semiconductor waveguides. © Springer International Publishing Switzerland 2014. Source


Tong X.C.,Laird
Springer Series in Advanced Microelectronics | Year: 2014

Polymer optical waveguides would play a key role in broadband communications, such as optical networking, metropolitan access communications, and computing systems, due mainly to their easier processibility and integration over inorganic counterparts. The combined advantages also make them an ideal integration platform where foreign material systems, such as yttrium iron garnet and lithium niobate, as well as semiconductor devices such as lasers, detectors, amplifiers, and logic circuits can be inserted into an etched groove in a planar lightwave circuit to enable full amplifier modules or optical add/drop multiplexers on a single substrate. Moreover, the combination of flexibility and toughness in optical polymers makes it suitable for vertical integration to realize 3D and even all-polymer integrated optics. This chapter would provide a brief review about polymer-based optical waveguides, including suitable polymer waveguide systems, their processing and fabrication techniques, and the integrated optical waveguide components and circuits derived from these materials. © Springer International Publishing Switzerland. Source


Tong X.C.,Laird
Springer Series in Advanced Microelectronics | Year: 2014

While developed for the needs of microelectronics, the silicon-on-insulator (SOI) wafers are excellent substrates for optical waveguides. SOI is a kind of structures formed by a thin layer of crystalline silicon (Si) on an insulating layer, which typically is silicon dioxide (SiO2). SOI optical waveguides possess unique optical properties due to the high transparency of silicon in the infrared spectrum and the large refractive index difference between silicon (guiding layer or core, n = 3.45) and SiO2 (insulator layer or cladding, n = 1.46). This high difference in indices of refraction strongly confines the electromagnetic field into the silicon layer. The widely used SOI waveguides may take the form of a channel waveguide, ridge waveguide, photonic-crystal waveguide, or slot waveguide. The photonic-crystal waveguide is an exceptional option for making SOI waveguides. The refractive indices of different areas of the cladding can be flexibly engineered by varying the diameter of the holes and the lattice constants. These excellent optical properties, as well as compatibility with silicon complimentary-metal-oxide semiconductor (CMOS) integrated technology, enable low-cost and dense optoelectronic integrated circuits. In fact, SOI material has become a main platform for both photonics and VLSI CMOS electronics, with fully compatible processing procedures. This chapter will give a brief review about the principle design, materials selection, and fabrication process of the SOI waveguides. © Springer International Publishing Switzerland 2014. Source


Tong X.C.,Laird
Springer Series in Advanced Microelectronics | Year: 2014

Hollow-core waveguides (HCWs) are comprised of a central hole surrounded by a highly reflective inner wall. The core can be filled with air, inert gas, liquid, or vacuum, allowing these waveguides to transmit a broad range of wavelengths with low attenuation. HCWs are of particular interest for the transmission of infrared (IR) to THz radiation, where it is otherwise difficult to find materials that have the optical, thermal, and mechanical properties required for use in solid-core optical fibers. Therefore, IR-transmitting hollow waveguides can be an attractive alternative to solid-core IR fibers. Hollow waveguides can be made from plastic, metal, or glass tubes that have highly reflective coatings deposited on the inside surface. These waveguides have losses as low as 0.1 dB/m at 10.6 mm and may be bent to radii less than 5 cm. For use in high-power laser delivery applications, the waveguides have shown to be capable of transmitting up to 3 kW of CO2 laser power. They are also finding uses in both temperature and chemical fiber sensor applications. This chapter will give a brief review about the progress in hollow waveguide technology with emphasis on the available hollow waveguides that have been developed. © Springer International Publishing Switzerland 2014. Source

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